To determine the scheduled repair/replacement timing of a part in a construction machine such as a hydraulic excavator, it is required to know the target repair/replacement time interval of the part and the past working time of the part. Heretofore, the target repair/replacement time interval of each part has been decided based on design data and experiences with a safety factor taken into consideration. Accordingly, the target repair/replacement time interval has been set to a slightly shorter interval. Also, the working time of each part has been calculated on the basis of the engine running time. As a result, the scheduled repair/replacement timing of parts has been calculated on the basis of the engine running time.
In a maintenance monitoring apparatus disclosed in JP,A 1-288991, for example, a time during which an engine is running (engine running time) is measured using a timer based on an output from a sensor for detecting the hydraulic pressure of an engine oil or an output from a sensor for detecting power generation of an alternator, and the engine running time measured using the timer is subtracted from the target replacement time of the relevant part, which is stored in a memory. Then, the resulted time difference is displayed on a display means. By checking the displayed time difference, each part including, e.g., oil and an oil filter, can be replaced without missing the proper timing of replacement of the part.